Curiosity Mastcam Left image acquired on Sol 1880, November 20, 2017.
Credit: NASA/JPL-Caltech/MSSS

Now in Sol 1882, NASA’s Curiosity Mars rover has wheeled to a new spot on the Red Planet.

A three-sol plan has been scripted, “all about picking interesting targets to explore at our Thanksgiving stopover point,” reports Claire Newman, Environmental Science Theme Lead/Keeper of the Plan for Ashima Research.

Newman explains that the plan also includes setting the robot up for winter “frost detection” experiments, and getting Curiosity’s Sample Analysis at Mars (SAM) Instrument Suite ready “to do some power-hungry analysis while we stay put.”

Curosity Front Hazcam Left B image taken on Sol 1881, November 20, 2017.
Credit: NASA/JPL-Caltech

Winter solstice

The Mars rover is just a few sols from southern winter solstice in Gale Crater on Mars, “which means it’s pretty much the coldest time of year and the best time for Curiosity to try to see water frost on the surface.”

If frost formation is observed, “this provides a lot of information for atmospheric scientists like me, who can use it to test models of when and how much frost should form on different types of surfaces, and to better understand how atmospheric water interacts with the surface and subsurface,” Newman points out. “The problem is that, even in winter, the temperatures in Gale only just dip below the frost point and then only right before dawn.”

Curiosity Mars Hand Lens Imager (MAHLI) photo acquired on Sol 1881, November 20, 2017.
Credit: NASA/JPL-Caltech/MSSS

Stay alert

Newman adds that in previous years of looking for frost, “we seem to have been unlucky…the last time we looked for winter frost, the experiment ran on what turned out to be the warmest night of the week. But this just means we have to stay alert to have a good chance of seeing it.”

Cool down

Science teams have chosen two targets to inspect: a small, smooth-topped sand patch, “Oaktree,” which sits in a kind of rock circle. Also targeted, a small rock with an east-facing slope called “Lebombo.”

“The sand should have a lower thermal inertia than rock, which means that it cools down more overnight and may be more likely to form frost,” Newman notes. “But porous sand can also tend to adsorb water instead of the water freezing on its top. So we also chose a rock target with an east-facing slope so it’s in shadow for as much of the afternoon as possible, which means it should be able to cool down a little more than other rocks overnight.”

Curiosity Rear Hazcam Right B image taken on Sol 1881, November 20, 2017.
Credit: NASA/JPL-Caltech

Hard to detect

Because Mars researchers only expect the frost layer at the rover’s location to be a few microns thick, and to vanish rapidly when temperatures start going up at dawn, it’s very hard to detect with cameras.

“So we’ll be using the ChemCam instrument and its Laser-Induced Breakdown Spectrometer (LIBS) to vaporize the top few microns of the surface at night and look for extra hydrogen in the signal, then compare this to daytime measurements of a similar location on the same target,” Newman says.

Curiosity Mastcam Right image taken on Sol 1879, November 18, 2017.
Credit: NASA/JPL-Caltech/MSSS

Just before dawn

On the plan, the robot was set to take daytime hydrogen measurements first, then in the next plan nighttime measurements are to be taken, just before dawn on Sols 1883 and 1886.

Newman says scientists are keeping their fingers crossed for seeing a big increase in the hydrogen signal on at least one of the targets.

“As well as the frost preparations,” Newman continues, “our new location stood out from a distance as having lots of color variety in Mastcam images, and we were able to access both brighter and darker blocks with the arm.”

Contrast of targets

On the Curiosity script is brushing bright target “Hexriver” to remove the top dust layer with the Dust Removal Tool (DRT) before ChemCam and the Alpha Particle X-Ray Spectrometer (APXS) are done, but the dark target “Zululand” was too small so no brushing will happen first.

Meanwhile, Curiosity’s Mastcam will be providing imaging of these targets, as well as documenting more of the light-gray/blue rocks that drew scientists to target “Natal” and the contrast between the bright and dark toned units on target “Kansa.”

Just before Sol 1880, the rover was to make Radiation Assessment Detector (RAD), Dynamic Albedo of Neutrons (DAN) and Rover Environmental Monitoring Station (REMS) measurements “to get a better idea of the aerosols – dust and water ice – around during the frost experiments,” Newman reports. And finally, the robot’s SAM instrument suite will be preconditioning overnight over Thanksgiving, preparing it to analyze samples from all the way back from the rover’s inspection of the Bagnold Dunes, she concludes.

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